How do I bake multiple texture maps into 1 UV, In Blender Cycles?
I found an alternate solution that's been working well with my tests.

Instead of baking my texture with my Diffuse, Gloss, and Normal maps linking to a principled shader leading to the material output for all the materials being used on 1 object as shown in the image during my question, I am now using individual texture types for each material and saving each bake as a diffuse, then adding those 3 diffuse maps directly into their appropriate fields in Unity, Diffuse, Specular, and Normal. 

Example:


UV unwrap the object to a new image
Wood Floor material > only has Diffuse texture node linked
Spackle Material > only has Diffuse texture node linked
Brick Material > only has Diffuse texture node linked
Add the above materials to the desired object faces
Bake texture as Diffuse with direct and indirect
lighting disabled and save the new image


This will be the full Diffuse map for the entire object


Swap out the above mentioned diffuse textures on every material with:


Wood Floor material > only has Normal texture node linked
Spackle Material > only has Normal texture node linked
Brick Material > only has Normal texture node linked
Create a new UV image for the bake to save to
Bake the new unwrapped texture, still as Diffuse with direct and indirect lighting disabled


Even though it's saved as diffuse, this will act as our normal map that we can simply drag and drop onto the objects material once it's in Unity.


Swap out the above mentioned diffuse textures on every material with:


Wood Floor material > only has Gloss texture node linked
Spackle Material > only has Gloss texture node linked
Brick Material > only has Gloss texture node linked
Create a new UV image for the bake to save to
Bake the new unwrapped texture, still as Diffuse with direct and indirect lighting disabled


Even though it's saved as diffuse, this will act as our gloss map that we can simply drag and drop onto the objects material once it's in Unity.

Repeat this process for any additional map types you want your finished mesh to have.